Process for producing 2 hydroxy-naphthalene-3-carboxylic acid

Abstract

A process for producing 2-hydroxynaphthalene-3-carboxylic acid comprising reacting carbon dioxide with a homogeneous liquid mixture comprising an alkali metal salt of beta -naphthol, beta -naphthol and a specific alkylbenzene is disclosed.

What is claimed is: 
     
       1. A process for producing 2-hydroxynaphthalene-3-carboxylic acid comprising reacting carbon dioxide with a homogeneous liquid mixture comprising an alkali metal salt of β-naphthol, β-naphthol and an alkylbenzene of the formula (I): ##STR3## wherein R is the same or different and is a straight or branched alkyl group having 1 to 4 carbon atoms and n is an integer of 1 to 6. 
     
     
       2. A process according to claim 1, wherein the formula (I) is the formula (II): ##STR4## wherein R' is the same or different and is a straight or branched alkyl group having 1 to 3 carbon atoms and m is an integer of 3 or 4. 
     
     
       3. A process according to claim 1, wherein the alkylbenzene of the formula (I) is diisopropyltoluene. 
     
     
       4. A process according to claim 1, wherein the molar ratio of the β-naphthol to the alkali metal salt of β-naphthol in the homogeneous liquid mixture is between 0.1:1 and 5:1 and the weight ratio of the alkylbenzene to the alkali metal salt of β-naphthol is between 0.1:1 and 5:1, respectively. 
     
     
       5. A process according to claim 1, wherein the molar ratio of the β-naphthol to the alkali metal salt of β-naphthol in the homogeneous liquid mixture is between 0.6:1 and 1.25:1 and the weight ratio of the alkylbenzene to the alkali metal salt of β-naphthol is between 0.1:1 and 1.0:1, respectively. 
     
     
       6. A process according to claim 1, wherein the preparation of the homogeneous liquid mixture is simultaneous with the formation of an alkali metal salt of β-naphthol and dehydration. 
     
     
       7. A process according to claim 6, wherein the preparation of the homogeneous liquid mixture involves dehydration in a fractionating column means. 
     
     
       8. A process according to claim 6 or 7, wherein the dehydration is performed at a temperature between 100° and 240° C. 
     
     
       9. A process according to claim 1, wherein the homogeneous liquid mixture is reacted with carbon dioxide at a temperature higher than 200° C. 
     
     
       10. A process according to claim 1, wherein the homogeneous liquid mixture is reacted with carbon dioxide at a CO 2  pressure less than 20 kg/cm 2  G. 
     
     
       11. A process according to claim 1 or 6, wherein (1) the reaction product is mixed with water or a mixture of water and an extraction solvent, followed by neutralization, extraction and separation into the aqueous layer and the organic layer, (2) the aqueous layer is subjected to extraction with an extraction solvent, followed by separation into the aqueous layer and the organic layer, and (3) the aqueous layer is treated with an acid to isolate 2-hydroxynaphthalene-3-carboxylic acid as a precipitate. 
     
     
       12. A process according to claim 11, wherein the extraction solvent is the same as what is used in the carboxylation. 
     
     
       13. A process according to claim 11, wherein the extraction solvent is a benzene compound that differs from the solvent used in the carboxylation. 
     
     
       14. A process according to claim 11, wherein the formation of the alkali metal salt of β-naphthol, dehydration, carboxylation, extraction and precipitation with an acid are performed continuously.